This comment letter response contains two parts:   

(1) The original submittal from the commenter.

(2) A data base printout of EPA’s response to each point raised by the commenter.

Notes about the response letters:

• The response letters were generated by a data base used to track the content of all public

comment submittals and ensure that the Agency responds to each. Each comment letter

was assigned a Letter ID that corresponds to the last four digits of the docket number of the

original comment (as posted on www.regulations.gov).

• Each response letter includes: comment text; an EPA‐assigned comment code; and an

individual response. These are described and explained below.  

• The data base contains Comment text from the letters submitted by commenters.  

Many hard copy letters were scanned into electronic format for inclusion in the data

base. As a result, there may be some typographical errors attributable to optical

character recognition issues.  However, all original submittals were reviewed in the

process of drafting responses to ensure that the comment content was understood and

appropriately addressed.

• The content of each comment letter was divided into topic areas and assigned a unique

Comment ID.  Additionally, one or more Comment Codes (i.e., unique topic area ID) was

assigned to each discrete point raised by a commenter. This information was added to

the data base. To inform final rulemaking decisions, all comments and information

received on a given topic were reviewed by technical experts in each rule area (e.g., on

construction requirements).  

• Following decisions on the final rule requirements, Individual responses were drafted

by topic area to ensure completeness and consistency of the responses with the final

rule and other responses to similar comments.  Each discrete point made by a

commenter was given a unique response.

• Upon completion of comment responses, all information was entered into the data base.

Each letter response is a compilation of each comment and its individual response,

compiled in the order of the original comment letter.  As a result of this process, there is

repetition in the response text.  The Agency believes this approach ensures completeness

and attention to each comment letter that was submitted.   

• All comments in a topic area were reviewed, evaluated, and responded to concurrently.  

Responses on each topic area are compiled and are also available in the rulemaking docket.
To: United States Environmental Protection Agency (EPA)

From: Kenneth J. Nemeth, Executive Director and Secretary, Southern States Energy Board

Principal Investigator, Southeast Regional Carbon Sequestration Partnership  

Date: December 23, 2008

Re: Docket ID No. EPA–HQ– OW–2008–0390, Comments on 40 CFR Parts 144 and 146 Federal

Requirements Under the Underground Injection Control (UIC) Program for Carbon Dioxide

(CO2) Geologic Sequestration (GS) Wells; Proposed Rule

The Southern States Energy Board (SSEB) serves to enhance economic development and the quality of

life in the South through innovations in energy and environmental policies, programs and

technologies. Sixteen southern states and two territories comprise the membership of SSEB.  

Representative of our efforts, SSEB manages the Southeast Regional Carbon Sequestration

Partnership (SECARB), a research program established in 2003 with the primary goals of identifying

major sources of carbon emissions, characterizing the geology of a 13‐state region, determining the

most promising options for commercial deployment of carbon sequestration technologies in the

South, and validating the technology options through carefully executed field testing. SECARB is one

of seven regional carbon sequestration partnerships nationwide, co‐funded by the United States

Department of Energy. SECARB’s membership is comprised of more than 100 active industry,

government, academic, and non‐profit participants.

Regarding injection issues, our areas of common interest within the partnership include:

• aquifer exemptions and prohibition on injection above underground sources of drinking

water (USDWs) (e.g. coal seams);

• credit for storage in enhanced oil recovery (EOR)‐related applications; and  

• transitioning from Class II EOR activities to storage only.

SSEB offers the following comments, which represent a consensus of thoughts shared by many of the

SECARB technical partners and stakeholders.  

The proposed Federal requirements under the Safe Drinking Water Act (SDWA) for underground

injection of carbon dioxide for the purpose of geologic sequestration is a step forward.  SSEB supports

the establishment of a new Class VI designation specifically dealing with GS. A new class of wells with

minimum technical criteria for the geologic site characterization, fluid movement, area of review

(AoR) and corrective action, well construction, operation, mechanical integrity testing, monitoring,

well plugging, post‐injection site care, and site closure for the purposes of protecting USDWs will

advance GS projects.  The proposed rule will help to ensure consistency in permitting of underground

injection of CO2 at GS operations across the United States and provide requirements to prevent

endangerment of USDWs in anticipation of the eventual use of GS to reduce CO2 emissions.  EPA’s

regulatory provisions should accurately reflect the low risk profile that exists for CO2 exposure from a

GS project.  
SSEB

Comments on EPA Proposed Rule, Docket ID No. EPA–HQ–OW–2008–0390

2

Importantly, under the proposed rule, EPA should specify that CO2 is not considered hazardous, nor

subject to regulation under RCRA or CERCLA, (while the rule recognizes that other gases could

contaminate the CO2, resulting in hazards to USDWs). Equally important, there should not be

limitations on formations that could be used for GS nor any depth limitations on injection zones. SSEB

does not support limiting a GS project beneath a sole source USDW aquifer or above the lowermost

USDW. These restrictions would only serve to limit a GS project from being sited in what would

otherwise be very safe geology. SSEB also does not support the requirement of secondary seals for

the same reason as stated above.    The only requirement would be viable provisions for safe and

secure containment to protect USDWs.

“Tailored requirements,” as opposed to more general or more specific requirements, are preferable

as they provide adequate protection while simultaneously allowing for the flexibility to address local

geology and site‐specific conditions and to embrace evolving technology. Tailored requirements

should be brought to bear when considering the nine specific topical areas for addressing the

proposed Class VI UIC requirements:

1. Geologic Siting;

2. Area of Review and Corrective Action;

3. Injection Well Construction;

4. Injection Well Operating;

5. Mechanical Integrity Testing;

6. Plume and Pressure Front Monitoring;

7. Recordkeeping and Reporting;

8. Well Plugging, Post‐Injection Site Care, and Site Closure; and  

9. Financial Responsibility and Long‐term Care.  

Regarding specific points, we concur with the establishment of a threshold of a seabed up to three

miles offshore, but no farther, and we support a requirement that the project operator should be able

to demonstrate that the CO2 is contained within the storage zone. We do not support the need to

monitor the exact location with in‐zone monitoring wells, the CO2 plume, or displace brine pressure

front.    CO2 monitoring should be fit for purpose.    Air and soil gas monitoring is unlikely to be

beneficial, and the use of tracers should be at the discretion of the owner/operator.   

Injection well construction details should be consistent with Class II CO2 EOR experiences and

operations and not unnecessarily burdensome to an owner/operator of a GS project.    Continuous

cementation from base to surface of the long‐string casing should not be required. No specific

timeframe for post closure care should be specified, and it should be based on performance standards

demonstrated by the owner/operator. Corrosion monitoring is unnecessary, as it would be assumed

that compatible well construction materials suitable for use with site‐specific CO2 composition would

be consistent.  

It is not useful to arbitrarily limit the depth of coal seams, since coal seams store CO2 via a very

different mechanism such that the required pressures are only a few hundred pounds per square inch

(psi) instead of many hundreds or thousands of psi.   The Southeast contains numerous oil and gas

fields that are potential safe geologic storage sites. SSEB encourages EPA to adopt a reasonable
SSEB

Comments on EPA Proposed Rule, Docket ID No. EPA–HQ–OW–2008–0390

3

process for EOR sequestration within Class II and EOR crossover to sequestration in oil and gas fields.  

Oil and gas fields are proven geologic sinks and contain much of the needed infrastructure for

efficient sequestration.  

Finally, it is important to note that there are other issues, such as liability, that are crucially important

to GS and which can impact GS projects, which are not covered under this proposed rule and

program.  

Thank you for the opportunity to provide comments on the Proposed Rule.   We would be glad to

provide additional input as you require.
Letter ID: 0176 

Commenter: Kenneth Nemeth 

Organization: Southern States Energy Board 

Letter ID: 0176 Comment ID: 23534 Letter Lines: 35 to 55 

Comment Code: 1000 1. General and Administrative Comments 

Comment: Representative of our efforts, SSEB manages the Southeast Regional Carbon 

Sequestration Partnership (SECARB), a research program established in 2003 with 

the primary goals of identifying major sources of carbon emissions, 

characterizing the geology of a 13-state region, determining the most promising 

options for commercial deployment of carbon sequestration technologies in the 

South, and validating the technology options through carefully executed field 

testing. SECARB is one of seven regional carbon sequestration partnerships 

nationwide, co-funded by the United States Department of Energy. SECARB’s 

membership is comprised of more than 100 active industry, government, academic, 

and non-profit participants. 

Regarding injection issues, our areas of common interest within the partnership 

include: 

- aquifer exemptions and prohibition on injection above underground sources of 

drinking water (USDWs) (e.g. coal seams); 

- credit for storage in enhanced oil recovery (EOR)-related applications; and 

- transitioning from Class II EOR activities to storage only. 

SSEB offers the following comments, which represent a consensus of thoughts 

shared by many of the SECARB technical partners and stakeholders. 

Individual Response: EPA acknowledges the comment. Please see the remainder of EPA's 

responses to this comment for further details. For additional information on EPA's final 

regulatory approach, please see the final rule and preamble, including the discussion of aquifer 

exemptions and the repermitting of Class II/EOR wells for GS, as well as the rulemaking docket. 

EPA clarifies that carbon crediting and green house gas accounting are outside the scope of the 

UIC GS rulemaking. The Class VI GS rule is designed to ensure consistency in permitting 

underground injection of CO2 at GS operations across the United States and provide 

requirements to prevent endangerment of USDWs in anticipation of the eventual use of GS to 

reduce CO2 emissions. 

Letter ID: 0176 Comment ID: 23535 Letter Lines: 57 to 69 

Comment Code: 1210 1.1.1 Comments about the proposed rule 

Comment Code: 2020 1.5.1 Support Class VI designation 

1
Comment: The proposed Federal requirements under the Safe Drinking Water Act (SDWA) for 

underground injection of carbon dioxide for the purpose of geologic 

sequestration is a step forward. SSEB supports the establishment of a new Class 

VI designation specifically dealing with GS. A new class of wells with minimum 

technical criteria for the geologic site characterization, fluid movement, area 

of review (AoR) and corrective action, well construction, operation, mechanical 

integrity testing, monitoring, well plugging, post-injection site care, and site 

closure for the purposes of protecting USDWs will advance GS projects. The 

proposed rule will help to ensure consistency in permitting of underground 

injection of CO2 at GS operations across the United States and provide 

requirements to prevent endangerment of USDWs in anticipation of the eventual 

use of GS to reduce CO2 emissions. EPA’s regulatory provisions should accurately 

reflect the low risk profile that exists for CO2 exposure from a GS project. 

Individual Response: EPA agrees that tailored requirements for Class VI wells are necessary to 

address the unique nature of injecting large volumes of CO2 and to ensure that USDWs are 

protected from endangerment. The GS rule contains tailored requirements for the permitting, 

geologic site characterization, AoR and corrective action, well construction, operation, 

mechanical integrity testing, monitoring, well plugging, post-injection site care, and site closure 

of GS wells that directly address issues unique to the nature of large-scale CO2 injection for GS. 

Letter ID: 0176 Comment ID: 23537 Letter Lines: 71 to 74 

Comment Code: 1630 1.3.3 RCRA/hazardous waste issues (seeking comment) 

Comment Code: 1640 1.3.4 CERCLA issues (seeking comment) 

Comment: Importantly, under the proposed rule, EPA should specify that CO2 is not 

considered hazardous, nor subject to regulation under RCRA or CERCLA, (while the 

rule recognizes that other gases could contaminate the CO2, resulting in hazards 

to USDWs). Equally important, there should not be limitations on formations that 

Individual Response: EPA received many comments regarding the applicability of the RCRA 

regulations and statute to CO2 streams that are geologically sequestered under the final Class VI 

UIC well requirements. As a result, EPA has decided to initiate a separate proposed rulemaking 

specifically to examine the issue of RCRA applicability to CO2 streams being geologically 

sequestered, including the possible option of a conditional exemption from the RCRA 

requirements for CO2 GS in Class VI wells. EPA will consider these comments as part of its 

development of that proposal. The Agency will consider issues particular to RCRA in the context 

of that separate rulemaking, and recommends that the commenter read that proposed rule when it 

is published. The Agency notes that commenters who wish to submit comments on the RCRA 

proposal will need to do so during the comment period for that rule. Finally, EPA also notes that 

the final GS rule, which adds new regulations for Class VI wells under the Safe Drinking Water 

Act (SDWA), is not making any changes to the RCRA regulations. 

With respect to CERCLA, EPA clarifies that CO2 itself is not listed as a hazardous substance 

2
under CERCLA; however, the CO2 stream may contain a listed hazardous substance (such as 

mercury) or may mobilize substances in the subsurface that could react with ground water to 

produce listed hazardous substances (such as sulfuric acid). Whether such substances may result 

in CERCLA liability from a sequestration facility depends entirely on the composition of the 

specific CO2 stream and the environmental media in which it is stored (e.g., soil or ground 

water). CERCLA exempts from liability, under CERCLA section 107, 42 U.S.C. 9607, certain 

“federally permitted releases” (FPR) as defined in CERCLA, 42 U.S.C. 9601(10). Class VI 

permits will need to be carefully structured to ensure that they prevent potential releases from the 

well which are outside the scope of the Class VI permit. 

Letter ID: 0176 Comment ID: 23538 Letter Lines: 74 to 75 

Comment Code: 2100 1.6 Target Geologic Formations for GS 

Comment Code: 4344 2.4.4.2.2 Comments opposed to setting a minimum injection depth 

Comment: to USDWs). Equally important, there should not be limitations on formations that 

could be used for GS nor any depth limitations on injection zones. SSEB does not 

Individual Response: EPA clarifies that the GS rule does not categorically preclude injection of 

CO2 into any non-USDW formation types. The purpose of the GS rule is to ensure protection of 

USDWs from endangerment, and the rule requires that owners or operators demonstrate that 

wells are sited in suitable systems with geologic formations to receive and confine injected CO2, 

required at §146.83 of the GS rule. The Class VI siting, well construction and operation, 

monitoring and testing, and post-injection site care and site closure requirements are designed to 

ensure that injected CO2 remains within the target formation. If an owner or operator can 

demonstrate to the Director's satisfaction that GS in coal seams, basalts, salt domes, or shales can 

be accomplished in a manner that protects USDWs and meets all of the requirements of the GS 

rule, the project may be permitted as a Class VI well. 

EPA agrees that it is not appropriate to set a minimum injection depth for GS projects. EPA 

believes that a determination of site-suitability for GS (i.e., that subsurface formations will 

receive and confine injected CO2) should be made on a site-specific basis. The GS rule, at 

§146.82, requires the owner or operator to provide extensive site- and project-specific 

information to the Director to demonstrate that the site meets the minimum site criteria at 

§146.83, that the CO2 will be contained within the injection formation, and that USDWs will be 

protected from endangerment. 

EPA acknowledges that there are limited circumstances where injection above the lowermost 

USDW can be performed in a manner that protects USDWs, as long as appropriate protections 

are in place. The final GS rule at §146.95 establishes a process by which owners or operators can 

seek a waiver of the Class VI injection depth requirements for injection into non-USDW 

formations above and/or between USDWs. The waiver approach requires the submission of 

extensive, site-specific information (in conjunction with the permit application submission) to 

demonstrate that injection of CO2 into a non-USDW that is above or between USDWs can be 

done in a manner that is protective of USDWs. The requirements are designed to ensure that the 

owner or operator, the Director, and the Regional Administrator consider, on a site specific basis, 

3
the implications, benefits, and challenges associated with GS and ensuring water availability and 

USDW protection. For additional information on the waiver approach, please see the final rule 

and preamble, as well as EPA's responses to comments on the Notice of Data Availability and 

Request for Comment. 

Letter ID: 0176 Comment ID: 23539 Letter Lines: 75 to 78 

Comment Code: 4324 2.4.4.1.2 Comments opposed to requiring injection below the lowermost 

USDW 

Comment: could be used for GS nor any depth limitations on injection zones. SSEB does not 

support limiting a GS project beneath a sole source USDW aquifer or above the 

lowermost USDW. These restrictions would only serve to limit a GS project from 

being sited in what would otherwise be very safe geology. SSEB also does not 

Individual Response: EPA acknowledges that there are limited circumstances where injection 

above the lowermost USDW can be performed in a manner that protects USDWs from 

endangerment, as long as appropriate protections are in place. The final GS rule at §146.95 

establishes a process by which owners or operators can seek a waiver of the Class VI injection 

depth requirements for injection into non-USDW formations above and/or between USDWs. 

Additionally, the final GS rule does not categorically preclude or prohibit injection into any type 

of formation. 

EPA believes that these requirements will ensure USDW protection while providing flexibility to 

UIC program Directors and owners or operators who undertake CO2 injection for GS. The 

Agency believes this approach: 1) responds to concerns about local and regional geologic storage 

capacity limitations imposed by the proposed injection depth requirements; 2) allows for a more 

site-specific assessment of injection depth for GS projects; 3) accommodates injection into 

different formation types; 4) allows for injection of CO2 for GS into non-USDWs above and/or 

between USDWs when appropriate and where it can be demonstrated that USDWs will be 

protected; and 5) responds to concerns about the use of aquifer exemptions for GS. Finally, 

EPA’s approach to addressing injection depth variability through a waiver process responds to 

concerns about future drinking water resource availability and the need to ensure that high 

quality water remains available in sufficient quantities to supply drinking water needs. For 

additional information on the waiver approach, please see the final rule and preamble, as well as 

EPA's responses to comments on the Notice of Data Availability and Request for Comment. 

Letter ID: 0176 Comment ID: 23540 Letter Lines: 78 to 81 

Comment Code: 3120 2.1.2 Need to identify additional confining and containment zones 

(seeking comment) 

Comment: being sited in what would otherwise be very safe geology. SSEB also does not 

support the requirement of secondary seals for the same reason as stated above. 

The only requirement would be viable provisions for safe and secure containment 

4
to protect USDWs. 

Individual Response: EPA clarifies that secondary confining zones are not required for all GS 

sites. Rather, secondary confining zones are required when the Director determines that these 

zones are needed to maximize the protection of USDWs from endangerment. EPA retains the 

requirement to identify additional containment/confining zones, if required by the Director, as 

proposed (e.g., §146.83(b)). EPA believes that, in some situations, the presence of additional 

confining and containment zones above the primary (i.e., lowermost) confining zone can 

improve USDW protection. These layers could further impede vertical fluid movement and 

allow for pressure dissipation, and also provide additional sites for monitoring, mitigation, and 

remediation. EPA disagrees that the requirement would reduce the number of sites available for 

GS. The intent of this requirement is to ensure that a proposed site provides adequate protection 

of USDWs from endangerment; if this protection cannot be demonstrated, the Director would not 

issue a permit for GS at the site. 

Letter ID: 0176 Comment ID: 23541 Letter Lines: 83 to 106 

Comment Code: 1250 1.1.1.4 Flexibility is needed (performance-based standards) 

Comment: "Tailored requirements," as opposed to more general or more specific 

requirements, are preferable as they provide adequate protection while 

simultaneously allowing for the flexibility to address local geology and sitespecific conditions and to embrace evolving technology. Tailored requirements 

should be brought to bear when considering the nine specific topical areas for 

addressing the proposed Class VI UIC requirements: 

1. Geologic Siting; 

2. Area of Review and Corrective Action; 

3. Injection Well Construction; 

4. Injection Well Operating; 

5. Mechanical Integrity Testing; 

6. Plume and Pressure Front Monitoring; 

7. Recordkeeping and Reporting; 

8. Well Plugging, Post-Injection Site Care, and Site Closure; and 

9. Financial Responsibility and Long-term Care. 

Individual Response: EPA agrees that permitting decisions for GS wells should be based on 

site-specific factors. The GS rule requires owners or operators to submit, and Directors to 

5
consider, extensive site-specific data, specified at §146.82, to demonstrate that a site is suitable 

for GS. Additionally, many of the permit requirements for GS wells are established through 

individualized site-specific plans for AoR and corrective action, testing and monitoring, and 

injection well plugging and post-injection site care and site closure. EPA adds that the final GS 

rule includes a balance of specific criteria to be met by the owner or operator and areas of 

Directorial discretion and considerations for how that discretion would be exercised. The Agency 

believes this balance allows for GS projects to be designed and permitted to address the unique, 

site-specific aspects of each project, while providing consistency in permitting across the U.S. 

Please see the final rule and preamble for additional information on EPA's final regulatory 

approach. 

Letter ID: 0176 Comment ID: 23542 Letter Lines: 108 to 113 

Comment Code: 4600 2.6 Proposed Plume and Pressure Front Monitoring Requirements (40 

CFR 146.90) 

Comment: Regarding specific points, we concur with the establishment of a threshold of a 

seabed up to three miles offshore, but no farther, and we support a requirement 

that the project operator should be able to demonstrate that the CO2 is 

contained within the storage zone. We do not support the need to monitor the 

exact location with in-zone monitoring wells, the CO2 plume, or displace brine 

pressure front. CO2 monitoring should be fit for purpose. Air and soil gas 

Individual Response: EPA agrees that the owner or operator should be able to demonstrate that 

CO2 is contained within the injection zone. For this reason, the final rule, at §146.90(g) requires 

owners or operators to perform CO2 plume and pressure front tracking. 

The final rule, at §146.90(g), requires owners or operators to perform monitoring to track the 

extent of the CO2 plume and pressure front. The owner or operator must use direct methods to 

monitor for pressure changes in the injection zone. Indirect methods (e.g., seismic, electrical, 

gravity, or electromagnetic surveys and/or down-hole CO2 detection tools) are required unless 

the Director determines, based on site-specific geology that such methods are not appropriate. 

Pressure monitoring in the injection zone is necessary to track the development and movement of 

the pressure front and CO2 plume. When combined with information on temperature, pressure 

data provide an indication of the phase (e.g., gas, supercritical) and distribution of the injected 

CO2 (73 FR 43515). Monitoring can also identify needed remedial actions, provide inputs for 

AoR reevaluation modeling, evaluate predictions of plume movement, and target additional 

geochemical and surface monitoring needs. 

EPA disagrees that knowing the location of the plume and pressure front is unnecessary; plume 

tracking and pressure monitoring are key components of monitoring at GS sites. A rigorous 

plume tracking and pressure monitoring scheme, such as one that meets the requirements at 

§146.90(g), is imperative for ensuring that the CO2 plume is contained within the injection zone. 

EPA clarifies that the limitation of the Class VI requirements not applying beyond the three-mile 

6
limit offshore reflects the UIC program's authority under SDWA. See the preamble for additional 

information about sub-seabed sequestration. 

Letter ID: 0176 Comment ID: 23543 Letter Lines: 113 to 115 

Comment Code: 4490 2.4.5 Use of tracers and potential impact on human health or ecosystems 

(seeking comment) 

Comment Code: 4670 2.6.7 Surface air monitoring and/or soil gas monitoring (seeking 

comment) 

Comment: pressure front. CO2 monitoring should be fit for purpose. Air and soil gas 

monitoring is unlikely to be beneficial, and the use of tracers should be at the 

discretion of the owner/operator. 

Individual Response: EPA acknowledges that air and soil gas monitoring to ensure USDW 

protection is not necessary at all GS sites and agrees that the decision to use surface monitoring 

and the selection of monitoring methods for the purpose of USDW protection will be sitespecific. 

The Agency believes that surface air and soil gas monitoring, when coupled with subsurface 

monitoring, may be appropriate at some GS projects to ensure USDW protection. EPA also 

acknowledges that surface air and soil gas measurements are subject to variability and may not 

be suitable in all settings as a method to ensure USDW protection. However, EPA does not 

believe that this should entirely preclude their use. The decision to use surface monitoring and 

the selection of monitoring methods will be site-specific (e.g., may be influenced by geology, 

injection depth, and operational conditions) and must be based on potential risks to USDWs 

within the AoR. 

If surface monitoring were the only monitoring method employed to ensure USDW protection, 

direct correlation of CO2 at the surface with CO2 in the subsurface might be difficult; however, 

when combined with information gathered through other monitoring techniques required of GS 

well owners and operators (e.g., monitoring wells, geophysical techniques), air and soil gas 

monitoring may provide valuable data on the magnitude and location of a leak. The CO2 itself 

may serve as a tracer in the form of stable isotopes of carbon. For example, anthropogenic CO2 

is depleted in 13C compared to naturally occurring CO2. 

In the final rule, at §146.90(h), the decision to require such monitoring as an additional measure 

to ensure USDW protection rests with the Director as a means of identifying leaks that may pose 

a risk to USDWs and informing emergency notification of a Class VI owner or operator and UIC 

Director in the event of a USDW endangerment, pursuant to requirements at §146.91(c). 

EPA agrees that the use of tracers may not be appropriate for all GS sites, but should be available 

as an option. For this reason, EPA does not require the use of tracers at all GS sites; however, the 

Director has discretion to require their use if he/she determines that the use of tracers could 

improve monitoring of the site and enhance USDW protection from endangerment. The rule will 

also allow their use if proposed by the owner or operator and approved by the Director. 

7
Letter ID: 0176 Comment ID: 23544 Letter Lines: 117 to 120 

Comment Code: 3824 2.3.1.2 Cementing of long-string casing (seeking comment) 

Comment: Injection well construction details should be consistent with Class II CO2 EOR 

experiences and operations and not unnecessarily burdensome to an owner/operator 

of a GS project. Continuous cementation from base to surface of the long-string 

casing should not be required. No specific timeframe for post closure care 

Individual Response: EPA believes that GS is sufficiently different from Class II ER operations 

to warrant the tailored construction requirements for Class VI wells at §146.86. For example, the 

volume of CO2 anticipated to be injected in Class VI wells is significantly greater than for Class 

II wells. Reservoir pressure conditions will be different, with Class VI injection operations 

involving large volumes of CO2 and likely having higher pressures within their storage 

formations than Class II ER projects. Therefore, Class VI GS reservoir pressures will increase 

more in comparison to Class II ER during the injection phase of the GS project. 

EPA recognizes that the oil and gas industry has decades of experience injecting CO2 for the 

purpose of enhanced recovery and that many of the wells used for ER may be suitable for GS. 

The final GS rule, at §146.81(c), allows the construction of these wells to be grandfathered, 

provided the owner or operator can demonstrate to the Director that the wells were engineered 

and constructed to meet the requirements at §146.86(a) and ensure protection of USDWs, in lieu 

of requirements at §146.86(b) and §146.87(a). Only the cemented-in-place construction 

requirements would be grandfathered under the final GS rule; following conversion, these wells 

must be permitted as Class VI wells and be subject to the operational, MIT, monitoring, 

reporting, plugging, and post-injection site care and site closure requirements in the final GS 

rule. 

The final GS rule requires, at §146.86(b)(2), that the surface casing must extend through the base 

of the lowermost USDW and be cemented to the surface, and that at least one long string casing 

must be cemented to the surface in one or more stages at §146.86(b)(3). It does not, however, 

specify how cementing must be accomplished, and it allows the owner or operator to propose 

alternate methods that provide a sufficient amount of cement to meet the standard that USDWs 

are protected from endangerment. EPA notes that there are many potential ways to meet the 

requirement, such as the use of staged cementing. Additionally, EPA is developing guidance on 

the construction of Class VI wells. This guidance will be available on EPA’s website at 

http://water.epa.gov/type/groundwater/uic/wells_sequestration.cfm. 

Letter ID: 0176 Comment ID: 23545 Letter Lines: 120 to 122 

Comment Code: 5240 2.8.2.2 Post injection timeframe (seeking comment) 

Comment: casing should not be required. No specific timeframe for post closure care 

should be specified, and it should be based on performance standards 

demonstrated by the owner/operator. Corrosion monitoring is unnecessary, as it 

8
Individual Response: EPA agrees with commenters that there will be circumstances where it 

can be demonstrated in less than 50 years that the plume and pressure front no longer pose a risk 

of endangerment to USDWs. For this reason, the final GS regulation offers owners or operators 

flexibility regarding the duration of the PISC timeframe by: (1) allowing the Director discretion 

to shorten or lengthen the PISC timeframe during the post-injection period based on site-specific 

data, pursuant to requirements at §146.93(b); or (2) affording the Director discretion to allow a 

Class VI well owner or operator to demonstrate, during the permitting process based on 

substantial data, that an alternative PISC timeframe may be appropriate if it ensures nonendangerment of USDWs pursuant to requirements at §146.93(c). 

EPA believes however, that to ensure USDW protection from endangerment, a default timeframe 

for post-injection site care will be necessary in most cases. The default 50 year post-injection site 

care timeframe represents a reasonable and protective monitoring period based on a review of 

research studies, industry reports, and existing environmental programs, and evaluation of public 

comments. 

EPA believes that a default post-injection site care timeframe of 50 years, with flexibility to 

adjust the timeframe for a limited number of GS projects during the permitting process where 

substantial data exists to demonstrate that an alternative timeframe would be protective of 

USDWs, or based on data collected during the PISC period, is appropriate to address the range of 

sites where GS is anticipated to occur, to accommodate site-specific circumstances and various 

geologic conditions, and addresses commenters’ concerns, while ensuring USDW protection. 

Both approaches will utilize site-specific data, and be based on pressure monitoring and USDW 

impacts. 

Letter ID: 0176 Comment ID: 23546 Letter Lines: 122 to 124 

Comment Code: 4250 2.4.3 Corrosion monitoring and control 

Comment: demonstrated by the owner/operator. Corrosion monitoring is unnecessary, as it 

would be assumed that compatible well construction materials suitable for use 

with site-specific CO2 composition would be consistent. 

Individual Response: EPA disagrees with commenter's assertions that corrosion monitoring is 

unnecessary or excessive. CO2 in the presence of water (including water with NOx, SOx, and 

H2S impurities) can be corrosive to well materials and cements. Thus, although a CO2 stream 

may be dry, the potential for corrosion of well materials down-hole, where the injectate can 

potentially mix with water in the target formation, must be considered. While the construction 

requirements at §146.86 were designed to protect against corrosion, EPA believes that multiple 

barriers against corrosion-related failures, including construction and monitoring requirements, 

are necessary in order to protect USDWs from endangerment. 

Several laboratory studies and a limited number of field studies have investigated and 

characterized the effects of carbonic acid on well materials. Laboratory studies (e.g., Kutchko et 

al., 2007; Kutchko et al., 2008; Akervoll, 2005) consistently identify alterations (typically 

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carbonation) of cement as the result of interactions between cement and CO2-saturated brine. 

Currently, there are only a few analyses of cement from wells that have been in prolonged 

contact with CO2 in actual field (down-hole) conditions. Evaluation of cement from a well at the 

Scurry Area Canyon Reef Operators Committee (SACROC) site showed alteration, but did not 

show degradation that compromised the structural integrity of the cement (Carey et al., 2007). In 

another study, cement samples were collected and analyzed from a CO2 production well in a 

natural CO2 reservoir in Colorado exposed to a CO2-water down-hole environment for 30 years 

(Crow et al., 2008). The study found evidence of reaction between the CO2-rich water and the 

cement. 

Oil industry research also addresses the effects of corrosion of steel tubing and pipes. Lopez et 

al. (2003) noted that 60 percent of oilfield failures are related to the effects of carbonic acid from 

produced brines on carbon and low alloy steels. A report by CO2 Norway (2004) notes that in 

some CO2 ER floods in the Permian Basin of Texas, bare carbon steel tubing has been used 

successfully. 

Laboratory investigation of cement alteration/degradation is an ongoing research area. Few fieldbased studies have been completed to date. Although the laboratory and field studies currently 

available suggest that corrosion problems may not be serious, there is not enough data to rule out 

potential corrosion problems of steel components of injection wells. Given the anticipated long 

lifespan of a Class VI well and the difficulties that would be associated with a corrosion-related 

well failure, EPA believes that corrosion monitoring in the down-hole environment is justified in 

order to protect USDWs from endangerment. 

Letter ID: 0176 Comment ID: 23547 Letter Lines: 126 to 133 

Comment Code: 2046 1.5.2.3 Continuing to classify CO2 injection for EOR/EGR as Class II/ 

dividing line between Class II and Class VI (seeking comment) 

Comment: It is not useful to arbitrarily limit the depth of coal seams, since coal seams 

store CO2 via a very different mechanism such that the required pressures are 

only a few hundred pounds per square inch (psi) instead of many hundreds or 

thousands of psi. The Southeast contains numerous oil and gas fields that are 

potential safe geologic storage sites. SSEB encourages EPA to adopt a reasonable 

process for EOR sequestration within Class II and EOR crossover to sequestration 

in oil and gas fields. Oil and gas fields are proven geologic sinks and contain 

much of the needed infrastructure for efficient sequestration. 

Individual Response: Regarding injection into coal seams, EPA agrees that the GS rule should 

not categorically preclude or prohibit injection into any type of non-USDW formation. EPA also 

acknowledges that there are limited circumstances where injection above the lowermost USDW 

can be performed in a manner that protects USDWs. The final GS rule at 146.95 establishes a 

process by which owners or operators can seek a waiver of the Class VI injection depth 

requirements. The waiver approach requires the submission of extensive, site-specific 

information (in conjunction with the permit application submittal) to demonstrate that injection 

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of CO2 into a formation that is above or between USDWs can be done in a manner that protects 

USDWs from endangerment. The requirements are designed to ensure the owner or operator, the 

Director, and the Regional Administrator consider, on a site specific basis, the implications, 

benefits, and challenges associated with GS and ensuring water availability and USDW 

protection. 

Regarding use of oil and gas fields for GS, EPA believes that the nature and risks of CO2 

injection for long term storage is different from Class II CO2 injection for ER, and that tailored 

requirements for GS wells are appropriate and necessary to protect USDWs from endangerment. 

For this reason, the Agency tailored UIC requirements for Class VI wells that address the general 

risks deep injection may pose to USDWs and specifically address the unique nature of CO2 GS 

(i.e., very large volumes, very long time-periods, and reservoir pressure conditions). 

EPA is developing guidance on transitioning permits from Class II to Class VI. The guidance 

will assist Directors in determining whether an injection project should be transitioned from 

Class II where the primary purpose is oil and gas production to Class VI where the primary 

purpose is long-term storage of large volumes of CO2. The guidance describes the methods 

available for the Director to evaluate changes in risk to USDWs from projects, and 

recommended approaches the Director may use to evaluate whether a project should be regulated 

within the Class II or Class VI UIC program. This guidance will be available on EPA’s website 

at http://water.epa.gov/type/groundwater/uic/wells_sequestration.cfm. For more information, 

please see the discussion on transition of Class II wells in the preamble to the final GS rule. 

Letter ID: 0176 Comment ID: 23548 Letter Lines: 135 to 137 

Comment Code: 5400 2.9 Proposed Financial Responsibility and Long-Term Care 

Requirements 

Comment: Finally, it is important to note that there are other issues, such as liability, 

that are crucially important to GS and which can impact GS projects, which are 

not covered under this proposed rule and program. 

Individual Response: EPA notes that SDWA does not contain any provisions addressing 

liability. 

Once an owner or operator has met all regulatory requirements under Part 146 for Class VI wells 

and the Director has approved site closure pursuant to requirements at §146.93, the owner or 

operator will generally no longer be subject to enforcement for regulatory noncompliance. 

Furthermore, their financial instrument as required under §146.85 will be released if it was not 

used. However, even if a site closure is approved under §146.93, an owner or operator may be 

held liable for regulatory noncompliance (including violation of 40 CFR 144.12) in certain 

circumstances. For example, an owner or operator may be held liable for regulatory 

noncompliance even after site closure was approved if the Director relied on erroneous 

information (e.g., erroneous modeling data) provided by the owner or operator when approving 

site closure. 

Separate from EPA’s authority to enforce regulatory compliance, an owner or operator may be 

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subject to a §1431 response order even after proper site closure is approved under §146.93. 

Under §1431 the Administrator may require an owner or operator to take necessary response 

measures if he or she receives information that a contaminant is present or is likely to enter a 

public water system or an USDW, which may present an imminent and substantial endangerment 

to the health of persons, and the appropriate State and local authorities have not acted to protect 

the health of such persons. The action may include issuing administrative orders or commencing 

a civil action for appropriate relief against the owner or operator of a Class VI well. If the owner 

or operator fails to comply with the order, they may be subject to a civil penalty for each day in 

which such violation occurs or failure to comply continues. 

The Agency clarifies that Class VI well permits may be transferred to another owner or operator 

pursuant to §144.38 whereby generally all other regulatory responsibilities are transferred to that 

new owner and operator, which includes all potential liabilities associated with meeting the 

requirements of that permit. Please see further clarification on the issue of long term liability in 

the preamble of the final rule. 

Furthermore, after site closure an owner or operator may remain liable under tort and other 

remedies, or under other federal statutes including, but not limited to, Clean Air Act, 42 U.S.C. 

§§ 7401-7671; CERCLA, 42 U.S.C. § 9601-9675; and RCRA, 42 U.S.C. § 6901-6992. EPA 

does not have authority to transfer SDWA or other legal liability for Class VI wells to the State 

or federal government or a third-party fund. See the final rule preamble for further discussion of 

EPA's final approach.